1. ## why p''=pp' ??

i have a function
y(x)

i want to substitute by variable p.

p=y'(x)=dy/dx

every derivative is by dx because its the smallest variable
so why

why dp/dy=p'

i cant see the meaning of derivative by y

??

2. Originally Posted by transgalactic
i have a function
y(x)

i want to substitute by variable p.

p=y'(x)=dy/dx

every derivative is by dx because its the smallest variable
so why

why dp/dy=p'

i cant see the meaning of derivative by y

??
I don't see what you question is, but as a dash denotes differentiation by $x$:

$
\frac{dp}{dy}=\frac{dp}{dx}\frac{dy}{dx}=p'p
$

CB

3. why we are doig a derivative by y

??

x is the smallest variable

4. Originally Posted by transgalactic
why we are doig a derivative by y

??

x is the smallest variable
x being the "smallest" variable makes no sense.